I've had MRIs post replacement. Not a problem because they put in non-conducting metal. The test my doc did to discover what was wrong with my knee was a nuclear bone scan. It showed what he called "a hot knee". It meant something was wrong with the knee itself and the surrounding areas. It lit up like a Christmas tree! Just another idea besides MRI. I have found with bones that MRIs don't always show what is wrong. Not sure why but that's just with me.